A wiper installed at such a front window or a rear window of various transportation means such as cars, trains, ships, aircrafts etc. comprises a wiper blade to sweep away droplets or dust adhered to a glass surface, and a wiper arm to support the wiper blade. At a contact portion of the wiper blade which contacts with glass, natural rubber has been mainly used, but other rubbers such as chloroprene rubber, styrene-butadiene rubber, EPDM (ethylene-propylene-diene copolymer) rubber or blended composition of these rubbers have also been used.
Recently, as a method to secure good driving visibility even in wet weather, a method to make a contact angle of water droplets adhering to the glass surface more than 90° by applying a water repellent agent on the surface of the glass and then forming a water repellent layer thereon has been widely used. The water repellent layer makes it easier for water droplets to slip off the glass surface when cars are stopped, and also makes it easier for the droplets to be blown off by the wind power generated on the glass surface when cars are driven, thus fairly improving visibility without frequent operation of wipers.
However, even after such surface treatment is finished, there still remains a need to sweep away foreign materials adhering to the glass surface by operating wipers for safer driving. But when the wiper is operated on the glass surface coated with the water repellent agent, the water repellent layer is gradually scraped away by repeated rubbing of the wiper blade, reducing deterioration in water repellency in a comparatively short period of time. Therefore, there was a need to frequently apply the water repellent agent on the glass surface. In addition, there has been a problem that if the wiper is operated when the water repellent layer is in the beginning of peeling, fluttering occurs in the wiper, which results in being unable to operate the wiper smoothly.
As a method to solve such problems, the inventors of the present invention learned that the lifetime of the water repellency of the water-repellent-agent-coated layer can be extended to be able to considerably reduce the frequency of applying the water repellent agent by using a silicone compound as the material of the wiper blade held by the wiper arm, thus being able to provide a wiper which is considerably improved in wiping properties when compared with the conventional one (JP-A-11-321573, JP-A-2000-160018).
As more and more requirements for quietness in transportation means are requested in these days, further improvements in sliding property as well as quietness of the sweeping operation are requested. The inventors of the present invention have provided a new wiper blade by adhering a powder to give a good sliding property to a lip portion of the wiper blade (JP-A-2000-55119). As a result, a wiper blade having an excellent sliding property and quietness has been practically used.